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The Road to Antihydrogen

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The Road to Antihydrogen The Road to Antihydrogen A thesis presented by Peter Spoor Yesley to The Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Physics Harvard University Cambridge, Massachusetts October 2001 2001 by Peter Yesley All rights reserved The Road to Antihydrogen Abstract Peter Yesley Thesis advisor: Professor Gerald Gabrielse Four advances were made towards the production of cold antihydrogen. First, a new mechanism of accumulating positrons was discovered and explained which increased our accumulation rate by over two orders of magnitude. Second, an intricate Penning trap was built to enable our group to study the antihydrogen formation process. Third, we demonstrated, for the first time, antiprotons cooling inside a positron plasma. And, finally, a detailed theoretical description of the dynamics of a charged particle in a Penning-Ioffe trap was developed. Contents Abstract................................................................................................................................. i Contents............................................................................................................................... ii Publications ........................................................................................................................ iv Acknowledgements ............................................................................................................ v List of Figures .................................................................................................................... vi Introduction ........................................................................................................................ 1 1.1 Motivations ......................................................................................................... 1 1.2 The Apparatus.................................................................................................... 5 1.3 Attempting Antihydrogen................................................................................. 8 1.4 Storing Antihydrogen........................................................................................ 9 Design and Construction of the ATRAP Trap............................................................ 11 2.1 A New Vacuum Enclosure............................................................................. 11 2.2 New Thoughts on High Voltage Isolation................................................... 15 2.3 Holding the Transmission Moderator .......................................................... 18 2.4 The Ball Valve ................................................................................................. 18 2.5 Passing Positrons Through the Ball Valve................................................... 23 2.6 The Source Elevator........................................................................................ 24 2.7 Electrical Connections .................................................................................... 28 2.8 Steering and Normalization: The PPAC ...................................................... 32 A New Mechanism for Positron Accumulation .......................................................... 36 3.1 Preparing the Moderators............................................................................... 37 3.2 New Mechanism for Positron Accumulation.............................................. 40 ii Attempting Antihydrogen .............................................................................................. 48 4.1 Preparing to Make Antihydrogen .................................................................. 48 4.2 Cooling Antiprotons with Positrons............................................................. 49 4.3 Pulsing and Catching Particles ....................................................................... 53 4.4 Proposed Initial Detection of Antihydrogen............................................... 57 4.5 Using the Fiber Detector While Loading Antiprotons .............................. 62 Trapping Antihydrogen ................................................................................................... 65 5.1 The Equations of Motion............................................................................... 66 5.2 Guiding Center Approximation..................................................................... 70 5.3 Applying the Guiding Center Approximation............................................. 71 5.4 The Series Expansion...................................................................................... 79 5.5 Numerical Calculations ................................................................................... 84 5.6 Adiabatic Invariants......................................................................................... 86 5.7 Experimental Quantities ................................................................................. 90 Diagram 5.1............................................................................................................. 93 Future Directions.............................................................................................................. 95 6.1 Simulating the Cooling of Antiprotons with Positrons.............................. 96 6.2 Rotating Wall and Plasma Density ................................................................ 97 6.3 Conclusion ...................................................................................................... 101 Bibliography ....................................................................................................................102 iii Publications 1. “Stability of a Combinded Penning-Ioffe Trap”, T.M. Squires, P. Yesley and G. Gabrielse, Phys. Rev. Lett. 86, 5266 (2001). 2. “The Ingredients of Cold Antihydrogen: Simultaneous Confinement of Antiprotons and Positrons at 4K”, G. Gabrielse, D.S. Hall, T. Roach, P. Yesley, A. Khabbaz, J. Estrada, C. Heimann, and H. Kaliowsky, Phys. Lett. B 455, 311 (1999) 3. “Field Ionization of Strongly Magnetized Rydberg Positronium: A New Physical Mechanisum for Positron Accumulation”, J. Estrada, T. Roach, J.N. Tan, P. Yesley, and G. Gabrielse, Phys. Rev. Lett. 84, 859 (2000). 4. “First Positron Cooling of Antiprotons”, G. Gabrielse, J. Estrada, J.N. Tan, P. Yesley, N.S. Bowden, P. Oxley, T. Roach, C.H. Storry, M. Wessels, J. Tan, D. Grozonka,W. Oelert, G. Scheppers, T. Sefsick, W. Breunlich, M. Carngelli, H. Fuhrmann, R. King, R. Ursin, H. Zmeskal, H. Kalinowsky, C. Wesdorp, J. Walz, K.S.E. Eikema, T. Haensch Phys. Lett. B 507, 1 (2001). iv Acknowledgements I would like to thank Gerald Gabrielse, my thesis advisor, for his support and effort in making this the best thesis possible - almost perfection. I’d like to acknowledge the crew of ATRAP: J. Estrada, J.N. Tan, N.S. Bowden, P. Oxley, T. Roach, C.H. Storry, M. Wessels, J. Tan, D. Grozonka,W. Oelert, G. Scheppers, T. Sefsick, W. Breunlich, M. Carngelli, H. Fuhrmann, R. King, R. Ursin, H. Zmeskal, H. Kalinowsky, C. Wesdorp, and J. Walz. Thanks for the help guys. I would like to salute Todd Squires who helped to create a new understanding. My most sincere gratitude for Janet Ragussa who on more than one occasion helped me to find things I did not even know I had lost. I want to acknowledge two people who when to great lengths to push my career forward, George Clark of MIT and Edward Fenimore of LANL. I would like to thank my parents, Irene and Michael. I would like to give special mention to my father for correcting the grammar of this thesis during the eleventh hour. Thank you to Maarten who provided enormous support; it is a shame he didn’t survive to read this. I would like thank Dorothea who has greatly increased the dimensions of my life. And finally, I would like to thank my best buddy in the whole world, Phillip, who kept me company during the greater part of this endeavor. v List of Figures Figure 1.1: The decay of the muon violates parity conservation because the mirror image of the process does not exsist in nature............................................................................ 2 Figure 1.2: Comparison of the accuracy of baryon, leptonand meson CPT test [3] ................. 3 Figure 1.3: The accuracies for the precise 1s-2s spectroscopy of antihydrogen are compared to the most stringent test of CPT invariance carried out with the three types of particles: mesons, leptons and baryons........................................................................ 5 Figure 1.4: The main components of the ATRAP I experiment. ............................................... 6 Figure 1.5: An overview of the ATRAP I instillation. ................................................................... 8 Figure 2.1: A comparison of the apparatus for LEAR and ATRAP ........................................ 13 Figure 2.2: A plot of the magnetic susceptibility of 70/30 copper nickel alloys at 4.2 Kelvin [15,16].............................................................................................................................. 14 Figure 2.3: The mechanical environment high voltage electrode.............................................. 16 Figure 2.4: The transmission moderator holder........................................................................... 17 Figure 2.5: Exploded view of the ball valve................................................................................... 19 Figure 2.6: The orientation of coils with respect to the field....................................................
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